I started doing Michael Mosley’s Blood Sugar Diet on 5:2 in July 2017. I allow up to 800 calories on Mondays and Thursdays and don’t count calories on the other days but I do follow the Mediterranean diet everyday – no refined carbs or sugars – and this may compensate for the higher calorie fast days. I also have 14 hours between dinner and breakfast everyday. The weight loss has been steady, 30 pounds over 12 months but it has also been easy and enjoyable and is a sustainable way of eating for maintenance now that I have reached my target weight. The health benefits are also noticeable, energy levels increased, fewer asthma attacks, less arthritis pain. I’d say give it a go! Good Luck.

@khog. All diets work…for a while. You have to find an eating pattern that is doable for the rest of your life. If you think 800cal and 5:2 and 14 hour fasts are doable forever going forward then go for it. Find a pattern that you can do. I do 6:1 and it incorporates a water fast for 36 hours. I find this doable and have been doing it for 3 1/2 years now. No longer for weight loss but for the health benefits. So my advice, find a pattern that you can do FOREVER.

Just incase you haven’t already tested these: Check that you are drinking enough on fast days, you need to up your fluids as a lot of our fluid intake is in our food, and you are having a lot less of that. Try to have a glass of water every waking hour. Also check that you are having enough salt to keep you hydrated, most diets are too high in salt, but on fast days you might be missing out. Soup/broth is perfect for liquid and salt! This may stop the headaches.

Re your actual question, if 800 calories makes the difference to make 5:2 sustainable, then do it. Remember this is a lifetime diet change, so keep at it once you reach your target healthy weight, so that you keep your target healthy weight.